For anyone not familiar with Nashville numbers, it is a charting scheme where the chord descriptions are based on the position rather than explicitly stated. In other words:
Most familiar to musicians is seeing chords written as follows (example): in the key of C major, the (“two” – second in the C scale) chord D minor 7 can be written as “dm7”, “2m7”, or “ii7”.
Using “Nashville Numbering”, in the key of C, C=1, D=2, E=3, and so on for all seven notes in the key. So, the chord progression
C///F///G///C/// would correspond to
This method of notation allows players (who must have a basic grasp of music theory) to play the same song in any key, thus avoiding re-charting during rehearsals or recording sessions.